3 years ago

HELP!!! when a person coughs, the trachea(windpipe contracts, allowing air to be expelled at max velocity. it can be shown that during a cough the velocity v of airflow is given by the function v=f(r)=kx^2(R-r) where r is the radius of the trachea in cm during a cough, R is the trachea's normal radius in cm, and k is a positive constant that depends on the length of the trachea. find the radius r for which the velocity of airflow is greatest.